Rectally absorbable form of L-dopa

Abstract

The invention relates to compositions and methods of enhancing rectal absorption of L-dopa via the formation of an ester prodrug and optionally with a decarboxylase inhibitor.

What is claimed is: 
     
       1. A method of enhancing the rate of absorption of a rectally administered composition comprising rectally administering to a patient a therapeutically effective dosage amount of an ester of L-dopa having the structural formula: ##STR2## wherein R is alkyl(C 1  -C 20 ), aryl(C 6  -C 9 ), unsubstituted aralkyl(C 7  -C 20 ) or pharmaceutically acceptable organic or inorganic counterion salts and pharmaceutically acceptable excipients. 
     
     
       2. The method of claim 1, wherein R is alkyl. 
     
     
       3. The method of claim 2, wherein said alkyl is selected from the group consisting of methyl, ethyl, isopropyl, pentyl, myristyl and palmityl. 
     
     
       4. The method of claim 3, wherein said alkyl is ethyl. 
     
     
       5. The method of claim 1, wherein R is aryl. 
     
     
       6. The method of claim 5, wherein said aryl is selected from the group consisting of phenyl and tolyl. 
     
     
       7. The method of claim 6, wherein said aryl is tolyl. 
     
     
       8. The method of claim 1, wherein R is substituted and unsubstituted aralkyl. 
     
     
       9. The method of claim 8 wherein said aralkyl is selected from the group consisting of benzyl, alkoxybenzyl(C 8  -C 14 ), phenylethyl, phenylpropyl, phenylisobutyl and phenyloctyl. 
     
     
       10. The method of claim 9, wherein said aralkyl is phenylethyl. 
     
     
       11. The method of claim 1, wherein said ester of L-dopa is in microenema or suppository form. 
     
     
       12. A pharmaceutical composition for enhancing rectal absorption of L-dopa by administering a formulation comprising a therapeutically effective dosage amount of an ester of L-dopa of the structural formula: ##STR3## wherein R is alkyl(C 1  -C 20 ), aryl(C 6  -C 9 ), unsubstituted aralkyl(C 7  -C 20 ) or pharmaceutically acceptable organic or inorganic counterion salts and suppository base or microenema excipients. 
     
     
       13. The composition of claim 2, wherein R is alkyl. 
     
     
       14. The composition of claim 3, wherein said alkyl is selected from the group consisting of methyl, ethyl, isopropyl, pentyl, myristyl and palmityl. 
     
     
       15. The composition of claim 14, wherein said alkyl is ethyl. 
     
     
       16. The composition of claim 12, wherein R is aryl. 
     
     
       17. The composition of claim 16, wherein said aryl is selected from the group consisting of phenyl and tolyl. 
     
     
       18. The composition of claim 17, wherein said aryl is tolyl. 
     
     
       19. The composition of claim 12, wherein R is substituted and unsubstituted aralkyl. 
     
     
       20. The composition of claim 19, wherein said substituted and unsubstituted aralkyl is selected from the group consisting of benzyl, alkoxybenzyl(C 8  -C 14 ), phenylethyl, phenylpropyl, phenylisobutyl and phenyloctyl. 
     
     
       21. The composition of claim 20, wherein said aralkyl is phenylethyl.